Rockport Quarry Limestone Explained

Rockport Quarry Limestone
Type:	Geological formation
Period:	Devonian
Unitof:	Traverse Group
Underlies:	Ferron Point Formation
Overlies:	Bell Shale
Thickness:	Approximately 14 meters

The Rockport Quarry Limestone is a geologic formation in Michigan. It preserves fossils dating back to the middle Devonian period.

Fossil content

Vertebrates

The Devonian vertebrate fauna of the Rockport Quarry Limestone is the most diverse in Michigan.

Cartilaginous fish

Cartilaginous fish reported from the Rockport Quarry Limestone
Genus	Species	Presence	Material	Notes	Images
Phoebodus	P. cf. P. sophiae	Alpena, Michigan.^[1]	A tooth.	An early elasmobranch.
?Tamiobatis	?T. sp.	"At the abandoned Kelly Island Limestone Quarry at Rockport State Park, Alpena County".	A single small spine (UMMP 13147).	A ctenacanthoid.

Placoderms

Placoderms reported from the Rockport Quarry Limestone
Genus	Species	Presence	Material	Notes	Images
Dinomylostoma	D. sp.			An arthrodire.
Dunkleosteus	D. sp.	Rockport Quarry, Alpena County.	A single incomplete right anterior ventrolateral (UMMP 16152).	An arthrodire.
Holonema	?H. rugosum		A single specimen (UMMP 3898).	An arthrodire.
	H. sp.		26 specimens.	An arthrodire.
Mylostoma	M. sp.		A single specimen (UMMP 13612).	An arthrodire.
Placodermi		At the abandoned Kelly Island Limestone Quarry at Rockport State Park, Alpena County.	2 specimens (7M, VP. 522.)	Placoderms of unknown affinity.
Protitanichthys	P. rockportensis		59 specimens.	An arthrodire.
Ptyctodus	P. sp.		A single specimen (UMMP 13045).	A ptyctodontid.

Invertebrates

Brachiopods

Brachiopods reported from the Rockport Quarry Limestone
Genus	Species	Presence	Material	Notes	Images
Chonetes	C. mediolatus		^[2]	Also found in the Bell Shale, Ferron Point Formation and St. Laurent Limestone.
Pentamerella	P. sp. B	Basal 8 inches of the formation.	2 specimens.
Pholidostrophia	P. gracilis gracilis			Also found in the Bell, Ferron Point and Genshaw formations.
Schizophoria	S. ferronensis	Basal 8 inches of the formation.		Also found in the Bell Shale, Ferron Point Formation and Silica Shale.
Schuchertella	S. crassa			Also found in the lower Bell Shale, Ferron Point Formation and Arkona Shale.
Spinulicosta	S. mutocosta			Also found in the Bell, Ferron Point, Four Mile Dam, Beebe School, Thunder Bay and Potter Farm formations.
Strophodonta	S. extenuata rockportensis	Lower 8 inches of the formation.
Tylothyris	T. rockportensis		^[3]	Appears to be endemic to the Michigan Basin.
	T. subvaricosa			Also found in the Cedar Valley, Milwaukee, Mineola, Bell, Ferron Point, Genshaw, Alpena, Gravel Point, Norway Point and Potter Farm formations.

Bryozoans

Bryozoans reported from the Rockport Quarry Limestone
Genus	Species	Presence	Material	Notes	Images
Fenestellidae	Species A		^[4]
	Species B
	Species C
Trepostomata	Species A
	Species B

Crustaceans

Crustaceans reported from the Rockport Quarry Limestone
Genus	Species	Presence	Material	Notes	Images
Ostracoda
Phlyctiscapha	P. rockportensis	Basal part of the formation.^[5]		An ostracod.

Molluscs

Molluscs reported from the Rockport Quarry Limestone
Genus	Species	Presence	Material	Notes	Images
Cephalopoda			"All specimens collected as single-hand specimens".
Gastropoda

Sponges

Sponges reported from the Rockport Quarry Limestone
Genus	Species	Presence	Material	Notes	Images
Clathrodictyidae
Idiostromatidae
Stromatoporidae

Trilobitomorphs

Plants and algae

Plants and algae reported from the Rockport Quarry Limestone
Genus	Species	Presence	Material	Notes	Images
Calcisphera	C. sp. A	"Abandoned quarry of the Onaway Limestone Company on the shore of Black Lake".
	C. sp. B	"Abandoned quarry of the Onaway Limestone Company on the shore of Black Lake".
Rhodophyta	Indeterminate	200 m south of the large sinkhole on the west wall of Rockport Quarry.
Vermiporella			"Observed as transverse sections, most specimens now irregular in shape due to crushing".

Cyanophytes

Cyanophytes reported from the Rockport Quarry Limestone
Genus	Species	Presence	Material	Notes	Images
Genus and species indeterminate	Indeterminate		"Spherical bodies 3-5 microns in diameter".
Oncolite				"Some post-depositional crushing of the sample has occurred".
Renalcis		"Abandoned quarry of the Onaway Limestone Company on the shore of Black Lake".

Foraminifera

Foraminifera reported from the Rockport Quarry Limestone
Genus	Species	Presence	Material	Notes	Images
Family indet.			"Found sparsely as solitary individuals in 6 specimens".
Nodosinellidae

See also

• List of fossiliferous stratigraphic units in Michigan

Notes and References

1. Swinehart . Anthony L. . Hoenig . Matthew M. J. . Ginter . Michal . July 2020 . A New Addition to the Devonian Elasmobranch Fauna of Michigan, U.S.A. . The American Midland Naturalist . 184 . 1 . 109–115 . 10.1637/0003-0031-184.1.109 . 31 January 2024 . 0003-0031.
2. Imbrie . John . 1959 . Brachiopods of the Traverse group (Devonian) of Michigan. Part 1, Dalmanellacea, Pentameracea, Strophomenacea, Orthotetacea, Chonetacea, and Productacea. Bulletin of the AMNH ; v. 116, article 4 . 2246/1258 . en-US.
3. Rogers . Frederick S. . Pitrat . Charles W. . 1987 . Distribution of Tylothyris (Brachiopoda) and Its Occurrence in the Traverse Group (Middle Devonian) of Michigan . Journal of Paleontology . 61 . 3 . 494–507 . 10.1017/S0022336000028651 . 1305304 . 130922140 . 0022-3360.
4. Cookman . C. W. . 1976 . Petrology of the Rockport Quarry Limestone (Middle Devonian Traverse Group) Alpena, Presque Isle and Montmorency Counties, Michigan . 130419618 . en.
5. Kesling . R. V. . 1953 . A New Beyrichiid Ostracod from the Middle Devonian Rockport Quarry Limestone of Michigan . 127104889 . en.